A large flock of vul­tures roosted in my cot­ton­wood trees last win­ter. The ground was solid white and the smell was not pleas­ant. Is roost­ing a sea­sonal event? If not, can I en­cour­age them to roost else­where?

Kenn and Kim­berly: Af­ter a day of work­ing as na­ture’s cleanup crew, vul­tures gather at night in com­mu­nal roosts. Un­for­tu­nately, once they find a good roost­ing site, they may re­turn year af­ter year. It’s il­le­gal to use lethal meth­ods on vul­tures, but it may be pos­si­ble to scare them away. Try dis­turb­ing them with loud noises or squirt­ing a wa­ter hose when they try to set­tle in for the evening, and they may seek an­other site. If they’re not so eas­ily dis­cour­aged, you might hire a pro­fes­sional an­i­mal-con­trol com­pany, but make sure they have a rep­u­ta­tion for op­er­at­ing le­gally and not harm­ing the birds.